Some types of explosive actuators, which are gas pressure actuators, have been used in various types of vehicles as shown in Patent Document 1. The explosive actuator includes a cylinder, a piston, and a gas generator. For example, when a collision detection sensor detects a collision, powders loaded in the gas generator are burned and the gas generator injects high pressure gas into the cylinder, which triggers a shift of the piston. As a result of this shift, the piston lifts the engine hood to ensure significant deformation of the engine hood in a pedestrian collision.